Uncovering the mystery of Al(III) doping of ε‐Fe₂O₃ in the ancient high‐iron black‐brown glaze

Abstract The world's first high‐fired glazes were made in China, probably in the 16th century BCE, based largely on siliceous clay and calcareous wood ash. By the Song Dynasty (960–1279), this technology was at its zenith and included blackware glazes that exhibited reddish‐brown single‐phase, micron‐scale ε ‐Fe 2 O 3 films on their surfaces. However, it has been difficult to synthesize and replicate this effect on a larger scale and to a higher degree of purity through modern synthetic methods. To fully understand this effect, a strategy that combines nanomaterial science methods and theoretical calculation has been developed to study the hare's fur glazes of Song Dynasty (960–1279) Jian wares. Through our study of the original Song glazes, we show that a high‐alumina clay was used in creating the glaze, which introduced Al into the ε‐Fe 2 O 3 lattices, playing a crucial role in metastable crystal stabilization. The explanation of both Al‐doping from clay, combined with a new understanding of ancient but effective firing manipulation, may provide alternative approaches for materials synthesis.